1. Field of the Invention
The invention relates to an apparatus and method for producing ultrasonic waves for non-destructive monitoring of a reactive material, specifically, monitoring for changes in material properties that designate the condition of the reactive material during reaction and service life.
2. Brief Description of Related Technology
Ultrasonic velocity measurements are capable of nondestructively detecting material property changes in reactive materials such as adhesives, sealants, and coatings. Measurements of reflected ultrasonic waves have been shown to be sensitive to the changes that occur in silicone gasketing during accelerated aging. The change in sound velocity determined from these measurements correlate with changes in shear modulus, lapshear strength, and chemical degradation. The failure of such reactive materials is often preceded by similar changes in material properties. The detection of these changes during the service life of a reactive material would allow precise prediction of when repairs or replacements should be made.
Ultrasound, depending upon the frequency, can penetrate up to several inches or feet of metal, plastic, or ceramic. Thus, the capability to measure the sound velocity of a gasket or any reactive material is a possibility. Therefore, with the appropriate selection of ultrasonic transducer and analysis site the sound velocity can be measured and used to monitor changes in materials properties that directly indicate the condition of the material. Difficulty in obtaining sound velocity measurements arise when the target material concealed behind or within another material. This is a common occurrence in the applications that utilized adhesives, sealants, or coatings where the obscuring material is referred to as a substrate. Additionally, the substrates maybe irregular in shape such that no relatively flat area that is parallel to the bond line is available. This is commonly the case in engines as parts are molded to fit next to complex and irregular shapes and contours. This may prevent the implementation of ultrasound monitoring as will be discussed further below. Therefore, a need arises for having a specifically designed analysis port along the substrate that is flat and parallel to the reactive material such that sound velocity measurements can be conducted.
U.S. Pat. Nos. 5,987,993 and 5,936,162 show an apparatus and method for non-destructive material testing using electrodynamically generated ultrasonic waves. These patents include providing one or more radio frequency coils disposed in a uniform magnetic field placed parallel to a surface of the workpiece. A number of horizontally polarized ultrasound waves are produced in the workpiece due to interaction of the magnetic field with the currents supplied by the radio frequency coil.
U.S. Pat. No. 5,670,879 discloses a non-destructive inspection device and method for monitoring defects inside a turbine engine. Specifically, an ultrasound transducer or an eddy current sensor is used to generate a signal indicative of characteristics of the rotating member of the engine. That signal is compared to a known signal representation to identify the existence of a defective condition in the rotating member.
None of these patents overcome the need of designing the boundary of contact area of the reactive materials to the substrate to facilitate the inspection of the adhesive material properties via ultrasound.